"Waterproof" sealant is what you'll need for exterior applications, and "Mildew-resistant" is a crucial characteristic of visible caulk used around moisture-prone areas such as showers and bathrooms. If you plan to paint the caulk bead, then look for "paintable" on your product package, because not all sealants will hold paint. Although silicone has long been a standard sealant for exterior doors and win- dows due to its elastomeric proper- ties, conventional silicone sealant will NOT accept paint, and the paint will simply bead up and bleed off the surface. "Paintable" caulks, however, will readily accept a new topcoat in your choice of color. Another note about silicone sealant: It tends to yellow over time. So if you don't plan on painting the
Standard silicone won't accept paint, which will simply bead on the surface without sticking.
If painting the bead, make sure your choice of product adver- tises its paintability like the bead of Lexel shown here.